Optical communication uses an optical signal to transmit information. In the optical communication, an optical fiber forms a waveguide for the optical signal. Often, there is a need to switch the optical signal from a first optical waveguide to a second optical waveguide.
A first method of switching a first optical signal uses a spatial light modulator and a plurality of lenses to selectively switch the first optical signal between a plurality of optical fibers. In the first method, a first optical fiber emits the first optical signal and directs the first optical signal to the spatial light modulator via a first lens. The spatial light modulator selectively reflects the optical signal to a second or third optical fiber via a second or third lens, respectively.
Because the first method requires alignment of the optical fibers, the lenses, and the spatial light modulator, it is relatively expensive to fabricate and loss of alignment will cause loss of efficiency. Further, because the first method employs geometrical optics to switch the optical signal, it occupies a relatively large space. Moreover, the first method requires sophisticated and expensive control circuitry to maneuver the spatial light modulator.
A second method of switching an optical signal uses first through third optical waveguides and a mirror. In the second method, a first end of the first optical waveguide aligns with a second end of the second optical waveguide. A third end of the third optical waveguide lies skew to the first end of the first optical waveguide. In operation, the mirror occupies a location selected from first and second positions. In the first position, the mirror rests in a gap formed by the first end of the first optical waveguide and the second end of the second optical waveguide. When the mirror is in the first position, a second optical signal exits the first optical waveguide, reflects from the mirror, and couples into the third optical waveguide. In the second position, the mirror rests outside the gap between the first end of the first optical waveguide and the second end of the second optical waveguide. When the mirror is in the second position, the second optical signal exits the first optical waveguide and couples into the second optical waveguide.
Because the second optical signal refracts out of the first optical waveguide and into either the second or third optical waveguide, tight tolerances are required to ensure that the second optical signal couples into the appropriate waveguide. Further because the second optical signal refracts out of and into waveguides, a portion of the second optical signal is lost due to reflection leading to inefficiency. This is because each refraction also includes a reflection loss.
What is needed is a method of switching an optical signal from a first optical waveguide to a second optical waveguide that is efficient and economical.